1. Technical Field
The present invention relates to a cylindrical rod. More particularly, the present invention relates to a cylindrical rod which is manufactured by bending sheet metal, and a method for manufacturing the same.
2. Related Art
A number of techniques have been developed to manufacture cylindrical products by bending sheet metal. One of those techniques is disclosed in Unexamined Japanese Patent Application Publication No. 2003-245721. According to the technique disclosed in this publication, relatively thin sheet matal is bent so that a tube with a small diameter is manufactured. In more detail, the above-mentioned publication suggests using a core roll that has substantially the same internal diameter as a target cylindrical product, a pair of pressing rolls that are pressed against the core roll so as to rotate together with the core roll, and a guide belt that is provided so as to connect the respective rolls and to form a unique path. With these rolls and guide belt, the sheet metal is shaped while being in a tight contact with the core roll. The above-mentioned publication explains that this technique enables the sheet metal to be shaped without causing barrel-like deformation.
Such cylindrical products may be desired to be utilized in place of solid metal round bars having a small diameter which are manufactured by means of the cutting technique, for the purpose of lowering the cost, for example. However, no cylindrical rod products have been developed which have satisfactory quality in terms of the characteristics such as the circularity of the circumference and the linearity in the axis direction.